| CPC H10N 30/883 (2023.02) [H10N 30/50 (2023.02); H10N 30/80 (2023.02); H10N 30/88 (2023.02)] | 9 Claims |

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1. A piezoelectric actuator comprising:
a piezoelectric element having a longitudinal direction;
a case configured to house the piezoelectric element inside, the case comprising
a lid portion,
a bottom portion, and
a tubular portion comprising a plurality of bent portions in the longitudinal direction, the plurality of bent portions each being configured to bend in response to extension and contraction of the piezoelectric element; and
a strain gauge positioned at the tubular portion at a bent portion of the plurality of bent portions.
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